Stable copolymer latex and paint comprising same



STABLE COPOLYMER LATEX AND PAINT COMPRISING SAIWE Robert L. Bebb, Akron, John H. Musch, Silver Lake, and James M. Willis, Akron, Ohio, and Verle A. Miller, Dover, Del., assignors to The Firestone Tire & Rubber Company, Akron, Ohio, a corporation of Ohio No Drawing. Application August 19, 1954, Serial'No. 453,412

28 Claims. (Cl. 26029.7)

This invention relates to an especially stable type of high styrene-low butadiene copolymer latex, which possesses unusual film-forming as well as adhesive properties. The invention also relates to an improved water dispersion paint embodying the improved latex. This application is a continuation-in-part of our copending application Serial No. 251,988, filed October 18, 1951, which is a continuation-in-part of our earlier application Serial No. 182,128, filed August 29, 1950, and now abandoned.

It has been proposed to incorporate a latex of natural or synthetic rubber into a water dispersion paint. These proposals have not proved to be commercially practicable, however, for various reasons. A film from any of the rubber latices heretofore available was soft and tacky; when the latex was mixed with paint pigments and a film of the resulting paint was dried, the film was soft and would not withstand washing with water.

Recently it has been proposed to incorporate certain copolymers of butadiene and styrene into water dispersion paints. The proposed polymers contained at least about '40 to 45% of butadiene. A film, cast from a latex of the proposed polymers, was soft and tacky, similar to the films previously cast from natural and synthetic rubber latices. Although a water dispersion paint comprising a latex of the proposed polymers was an improvement over previous paints containing a rubber latex, it still failed to produce a dried paint film of sufficient hardness to compete successfully with oil base paints.

Therefore, it is an object of the invention to provide an improved synthetic polymer dispersion suitable for incorporating into a water dispersion paint. Another object is to provide an improved Water dispersion paint giving paint films of sufiicient hardness and gloss to compete successfully with oil base paints. Another object is to provide an improved method of polymerizing and stabilizing a synthetic polymer dispersion, and to provide the improved stabilized latex. The above and other objects will become apparent in the description of the invention which follows:

The improved synthetic polymer dispersions of the invention are produced by copolymerization of 1,3-butadiene and styrene in fixed proportions and under specific and critical conditions. in order to produce continuous films of the desired hardness it has been found necessary that the copolymer contain no more than 39% and not less than 27% butadiene. It has been found that films cast from polymer dispersions containing 40 or more percent butadiene, though continuous, are too soft and tacky. Dispersed polymer containing more than 73% styrene will not form continuous films-only a powder results. Continuous hard films, however, are produced from all the dispersed polymers containing no more than 39% and not less than 27% butadiene. Relatively large amounts of a persulfate as an initiator are required. At least 0.65 and preferably from 1.0 to 2.0 parts by weight of persulfate per 100 parts of monomer should be used. The polymerization systems contemplated contain very small proportions (0.02 to 2.5 parts by weight per 100 parts by weight of monomer) of emulsifier initially charged in the reactors. Suitable emulsifiers are the alkyl and alkaryl sulfonates, alkyl sulfates and salts of naphthenic acids. Polymerization in accordance with the invention is effected in either an acidic or basic system. Since, however, it is often inconvenient to use acid-resistant equipment, it is often desirable to adjust 'the pH of the polymerization system by bufier addition United States Patent I 2,702,285 Patented Feb. 15, 1955 to a pH of 7.0-l2.0 and preferably 8.0l0.0. Suitable buffers are NazBrOIlOHzO, NaOH-l-HBOg, NaBOz, NazHPO4, NasPOr, and Na4P2O1. Other buffers may be used such as carbonates and bicarbonates.

Illustrative formulations of the invention having diffenng proportions of butadiene and styrene appear in Examples 1-4 which follow. Polymerization ingredients in accordance with the recipes shown in Table l were charged into 28 oz. crown capped glass bottles. The bottles were then capped and rotated end over end in a 50 C. water bath for 45.5 hours to produce the polymen zations shown in the table. All quantities of ingredients are shown as parts by weight.

TABLE 1 Example No 1 2 3 4 Butadleue 65 70 75 80 Styrene.-- 135 130 125 Water 300 300 300 300 K2520: 3.2 3. 3.2 3.2 Narmg ggnron 2. 0 2. 0 2. 0 2.0

0 4 After 45.5 hours: 0 4 0 4 0 4 Total Solids, percent..- 39. 6 40. 1 40. 1 37. 6 Percent Conversion.. 96. 0 100. 0 100. 0 90. 0 H 8.3 8. 4 8.2 8. 9

An alkyl sodium sultonate supplied by E. -I. du Pont de Nemours 6: Company.

Further formulations having still higher proportions of styrene were polymerized under slightly different conditrons in accordance with the recipes shown in Table 2. All quantities of ingredients are shown as parts by weight.

an alkaryi sulionate supplied by National Aniline Division of the Allied Chemical and Dye Corporation.

"The N acconol was injected by a hypodermic needle into the reaction mixture at about 60% conversion.

Films were cast from the resulting aqueous polymer dispersions of Examples l-7. Excellent continuous, clear,

hard films resulted from the dispersions of Examples 1,

2, 3, 5 and 6. The film from Example 4 was somewhat soft. The film from Example 7 was brittle.

An important characteristic of the copolymer latices of the invention is the low surface value of the dispersed latex particles. The surface values of the latices may conveniently be expressed as specific surfaces. The lowest specific surface value observed for a latex of the invention was in the order of 3 square meters per gram of the dry copolymer. Many of the preferred latices possessed specific surfaces in the range of about 9 to about 43 square meters per gram, the upper limit appearing to be about 60 square meters per gram.

The improved copolymer latices of the invention possess good stability, especially mechanical stability. They may be applied, as by dipping, spraying or spreading, to most surfaces to coat the surface with a film which dries to a smooth, hard, continuous coating. The dried film is transparent or substantially transparent, and it is resistant to washing and abrasion.

The copolymer latices may be mixed with most of the common paint pigments to produce a paint or coating composition of the water dispersion type, which dries to form an opaque film. The pigments may be added as dry powders to the latex if sufiicient precautions, known to the art of compounding natural rubber latex, are taken to avoid coagulating the latex. However, it is preferred talc and zinc sulfide.

. dispersing agent,

that casein can be readily made dispers1ble 1n water by treating it with a Water solution of an alkalme material,

presence of a dispersing agent for the production of a water dispersion of thepigments suitable for mixing with the latex. Many of the dispersing agents known to the colloid art may be utilized, including the various water solubl'e soaps, the aliphatic or aromatic sulfonates, the

sulfolignins, the alFphatic sulfates, and other anionic emulsifying agents on the market; various poly-others, ether-alcohol condensates and other nontonic emulsify ng agents; and the various hydroplulic colloidal dispersing agents, including casein, soya bean protein and other animal and vegetable proteins (including albumens) capable of reacting with an alkaline material to become dispersible in water, cellulose ethers, such as methyl cellulose, and other water dispersible cellulose derivatives, as well as other hydrophlic colloids well known in the colloid art. Two or more dispersing agents may advantageously be used in a single paint.

Typical paint pigments which may be successfully 1ncorporated with the copolymer latex into a paint include titanium dioxide (the anatase or rutile grade is satisfactory), clay, silica, lithopone, mica, barium sulfate, Many dyes and colored pigments may be included in the pigment formulation, including carbon black, iron oxides, cadmium yellows, phthalocyanines, ultramarine, chromium oxides, umber and sienna. An example of a satisfactory paint of the flat interior type is a white paint utilizing caseinias the pigment It is wel known in the paint industry including ammonium, sodium or potassium hydroxide or an alkaline salt such as borax, sodium or potassium carbonate. f For example, parts of dry casein are added to 56 parts, by weight, of soft water, and the mixture is allowed to stand at ordinary room temperature for 30 to 60 minutes. Then the mixture is stirred and warmed to about 60 C. One part of borax is added to the warm mixture with stirring, and the mixture is stirred for an additional 30 minutes at 60 C. The casein dispersion is allowed to cool. Preferably a fungicide is added to the casein dispersion'to protect it and the'resulting paint from the mold, etc.; e. g., 2 to 3 parts of a solution of Dowicide A* (and a corresponding reduction of the original water, employed for dispersing the casein, from 56 to 53 or 54 parts) may be added to the cool casein dispersion.

A paint may be prepared in accordance with the following formula:

. freeze stable dispersions.

Ingredients: Parts by weight Pigment(s) 20 to 40 Water 14 to 30 Casein dispersiun 1 to 10 Antifoaming agent 0.75 to 3 Copolymer latex 20 to 55 A somewhat more detailed formula may be:

Ingredients: Parts by weight Titanium dioxide 2 to 25 Lithopone 3 to 12 Silica and silicates; 4 to 12 Color (if desired) 3 to 12 Water 14 to 30 Protein'dry (as a dispersion) 1 to 3 Antifoaming agent 0.75 to 3 Polymerized oil 1 to 6 Copolymer latex 25 to 55 The ingredients maybe chosen in the ranges shown in the-above formulas, depend ng upon the specific paint properties desired. The paint may be prepared- Sodium salt of ortho-phenyl phenol.

4 added. Additional fungicide, amounting to 1 to 2 parts, may be added at this point to improve the resistance of the paint to fungi. attack. Then the copolymer latex is carefully added, with slow stirring, so as to avoid formation of foam, and the paint is slowly stirred for an additional period of 15 to 30 minutes. The mixed paint may then be filtered, if desired, and is ready for use or packaging.

Dispersion paints, since they contain water, necessarily freeze when they are subjected to low temperatures, as for example temperatures normally occurring during the winter. Aqueous polymer dispersions,

ordinarily available commercially, coagulate when allowed to thaw after having been frozen despite additrons of known stabilizers. Dispersion paints containtng such polymer dispersions, if frozen and thawed,

will also tend to coagulate, and thus cannot be brushed or otherwise applied to a surface to be painted. Shipping and storing of such paints must, therefore, be

carefully regulated in order to prevent freezing of the purpose may be selected from the anionic emulsifiers, nomonlc emulsifiers and mixtures of anionic and non- IOIllC emulsifiers. Excellent dlspersion paints which are also freeze stable may be prepared by incorporating paint pigments into these stabilized polymer dispersions.

In the specific examples which follow, freeze stabilities of polymer dispersions were determined by placing 50 ml. samples of the polymer dispersions in 125 ml. Erlenmeyer flasks. The flasks were then stoppered and placed in a freezing chamber where they were maintained at -l8 C. for 3 hours. The flasks were then removed from the freezing chamber and the frozen contents allowed to thaw at room temperature. The contents were then observed to determine their freeze characteristics. Poor freeze characteristics were reflected by coagulation of the polymer dispersion. A polymer dispersion having good freeze stability did not coagulate but remained mobile and fluid.

Freeze stability of dispersion paints containing aqueous polymer dispersions was determined in a somewhat similar manner as follows: Thirty grams of dispersed pigment and 20 g. of stabilized aqueous polymer dispersion were weighed into V4 pint metal cans. Viscosity of the resulting paint was adjusted by adding water until the paint possessed a viscosity of 6 seconds as measured in 'a conical brass cup, capacity ml., with a bottom orifice 0.277 inch in diameter. Viscosity according to this test was determined by filling the cup with paint and measuring the time in seconds required for the paint to flow through the cup orifice until the stream of paint broke. The metal cans were covered and placed in a freezing chamber where they were maintained at 30 C. for 16 hours. The cans were then removed from the freezing chamber and the contents allowed to thaw at room temperature. When the contents of the cans had reached room temperature, the contents were observed in order to determine their freeze characteristics. If the contents had coagulated, the paint had failed the test. If the contents had not coagulated, freeze characteristics were evaluated by observing viscosity and grain (floc) presence. Increased viscosity and increased amounts of grain indicated decreasing freeze stability. When freeze characteristics had been observed after one freezing and thawing cycle, the cans were again covered and the contents subjected to succeeding identical cycles until the contents coagulated or exhibited poor stability, or had been subjected to four freezing cycles. Some freeze stability is reflected by a paint which does not coagulate after one cycle. Exceptional freeze stability is reflected by a paint which has a viscosity of no more than 30 seconds and contains no grain' after 4 freezing cycles.

Freeze stable polymer dispersions Representative specific examples" of polymerizations Suitable emulsifiers .for this of the'invention were carried out in accordance with the polymerization formulae shown in Table 3. All of these formulae include, additionally, butadiene and styrene in the ratio 37:63 parts by weight. The proportion of persulfate catalyst utilized in these polymerizations was essentially the only variant. The proportions of borax represent only the theoretical quantities required to neutralize free acid formed during polymerization. All polymerizations were made at 70 C. All quantities are shown as parts by weight per 100 parts of monomer.

After polymerization was completed, each of the resulting polymer dispersions was further stabilized by adding thereto a mixture of emulsifying agents consisting of 1.2 parts by weight per 100 parts of polymer of Nacconol NRSF and 1.0 part by weight of each of the following: Triton X-l00 GMR--S and ammonium oleate. Freeze characteristics of the thus stabilized polymer dispersions were determined according to the sion to add additional emulsifier at some time late in the polymerization in order to produce a more stable polymer dispersion. It has been found possible to make such an increment addition of emulsifier without detracting from the freeze stability, provided the addition is not made earlier than about 50% conversion.

A plant scale polymerization was made of the following initial ingredients:

Parts b wei t Butadiene y 37 Styrene 63 X28208 1.2 MP-189-S 0.56 Na2B407JOH2O 1.48 Water initially charged 145 Polymerization was effected at 70 C. At about 60% conversion 2.2 parts by weight of Nacconol NRSF was injected into the reactor and polymerization completed.

procedure outlined above and are also recorded in A small amount of unreacted butadiene was removed Table 3. from the resulting latex by stripping in accordance with TABLE 3 Specific Specific Example msioi MP-ISQ-S Nmmotromo Water Swim Character- No. sq.m./g.dry istics polymer 1. 3 0. 1 1.8 120 35.1 Good. 1.6 0.1 as 120 29.1 Do. 20 0.1 as 120 22.3 Do.

' An alkyl sodium sulfate supplied by E. I. du Pont de Ncmours & Company.

Additional polymerizations in accordance with the incommercial synthetic rubber practice. The polymerized vention were made with the recipes shown for Examples 11 to 17 inclusive set out in Table 4. All polymerizations contained butadiene and styrene in the ratio 37:63 and all polymerizations were carried out in the presence of 1.6 parts by weight of KzSzOs. Essentially the only variant was the amount of emulsifier initially charged in the reactors. All quantities are shown as parts by weight for 100 parts of monomer. After polymerization, each of the resulting polymer dispersions was further stabilized by the addition thereto of 2.2 parts of Nacconol NRSF and 5.0 parts of morpholinium salt of Resin 731*. Freeze chajracteristics were examined and are also recorded in Ta le 4.

dispersion possessed a pH of 8.8. The specific surface of the dispersion was 38.5. Samples of the resulting polymer dispersion were further stabilized by the addition of a stabilizing mixture of emulsifying agents consisting of 1.0 part by weight per 100 parts of polymer of each of the following: Triton X-l00, GMR-S, and ammonium oleate. When the resulting stabilized dispersions were subjected to the previously outlined freeze tests they were found to be very fluid and mobile.

Freeze stable paints Dispersion paints were produced by adding the stabilized polymer dispersions of Examples 8, 9, 10 and 18 TABLE 4 Freeze Tampa Iime for Percent Characterffi MP-lSQ-S azure, NazBio-r. 1011.0 Water gfggg g F 133 liffi f 111 Hours Solids Polymer Dispersions 0. 02 1. 2 150 16. 0 Good. 0. 10 2. 3 120 10. 5 44. 5 D0. 0. 30 70 2. 3 120 8.0 44. 1 D0. 0. 50 70 2. 3 120 8. 0 44. 4 D0. 0. 70 2. 3 120 8. 0 45. 8 D0. 1. 00 70 2. 3 120 8.0 44. 9 Do. 1. 30 70 2. 3 120 9. 5 45. 0 Do.

A control polymerization containing no emulsifier, but other ingredients and conditions identical with Example 11, required 39 hours for polymerizing to complete conversion. Referring to Table 4, it can be seen that very short reaction times result from the small amounts of emulsifiers initially charged into a reactor in accordance with the invention. Stabilized polymer dispersions from all of the examples possessed excellent freeze characteristics and remained mobile and fluid after the rigorous freeze tests.

EXAMPLE 18 It has been found desirable in order to obtain freeze stable polymer dispersions to keep the amount of emulsifier initially charged into a polymerization reactor at a minimum. However, it may be advantageous on occa- An alkyl aryl polyether alcohol which is a nonionic emul- Slfied and is supplied by Rohm & Haas Company.

A soap modified glyceryl monoricinoleate supplied by Glyco Products Company.

Resin 731 is a. disproportionated rosin supplied by Herculea Powder Company.

to paint pigment dispersions prepared in accordance with the detailed discussion above. The resulting paints were examined for freeze stability according to the previously outlined procedure. Freeze characteristics of the paints produced from Examples 8, 9, 10 and 18 are shown R;- spectively in Table 5 under the headings of Examples 19-22.

pigment dispersions with aqueous polymer dispersions produced by polymerizing the ingredients shown in Table 6.

a All of the Examples 23-26 contained butadiene and 8 5 part by weight at 33% total solids and 0.6 part by weight at 38.7 total solids. unreacted butadiene was stripped; and 1.0 part by weigh of Triton X-l was added to the polymer dispersion.

styrene in the ratio 37:63 and were polymerized at 70 Separate portions of the resulting dispersion were fur C Two and two tenths percent Nacconol NRSF was inther stabilizedby adding the following mixtures'of emuljected into the reactors during all of these polymcrizaslficl'si tions at 60-75% conversion. Final total solids of the. v Parts by weight resulting polymer dispersions were in the range 40-45%. per 100 parts of polymer After polymerization was complete, the polymer dis- 10 Example 291 rsions of Examples 24 and 26 were further stabilized 7 GMR4 1.0 the addition thereto of 1.5 parts by weight of Triton Ammonium 1.0 X-lOO and 1.5 parts by weight of Antarox A-400, both Example 30: per 100 parts by weight of polymer. The dispersions of GMR-S. the other examples were stabilized. after polymerization gi e. by the stabilizing mixture used in Example 18. Freeze Ycery monol'lcmoleam-ue 2,0 characteristics of the resulting paints were determined and The stabilized polymer dispersions of Examples 29 and are also showninTable 6. 30 were then mixed with identical paint pigment disper- TABLE 6 Water Eig gli mgm; MP-189-B N82B401JOH2O initially First Freeze Cycle Later Freeze Cycles charged Polymer 23 1.0 0.47 1.23 145 30.0 Viscous, very slight Coagulsted after second gram. cycle. 1.3 0.3 1.8 110 33. 2 Fluid, no grain Mobile without agitation, fluid and no grain after 4th cycle. 1. o 0.8 2. 2 130 32. 1.6 2.5 2.3 120 9.6 Moderately viscous, no

grain after 4th cycle.

Two additional dispersion paints were prepared by mixsions and the resulting paints were subjected to the freeze ing paint. pigment dispersions with aqueous polymer distest. The freeze characteristics follow: persions produced'in accordance with the recipe and conditions of Example 18 except for further stabilization after 1 7 Later Freezm polymerization. One of the polymer dispersions (Ex- Freezing Cycle Cycles 8 ample 27) was further stabilzzed) by thefa ldditiogcolfog 40 stabilizing mixture consistingo parts 0 riton J t and 3.0 parts of ammonium salt of Resin 731, both by Fxamplezg Viscous slight gram tflhiiffii on see weight per 100 parts of polymer. The paint produc d Example30 Mode ately viscous, trace Viscous, heavy grain. from this stabilized polymer dispersion was only slightly grainthird cycle-i viscous and contained no grain after 4 freezing cycles. The other polymer dispersion (Example 28) was further The paint of Example 30 was considerably more freeze stabilized after polymerization by the addition of a stabiresistant than the paint of Example 29. Another stabilizlizing mixture consisting of 3.0 parts of Triton X-100 mg mixture very suitable for addition after polymerizaand 3.0 parts of the ammonium salt of linseed oil fatty tion consists of 1.5 to 3.0 parts by weight of Triton X-lOO acid, both by weight per 100 parts of polymer. The and 3.0 parts by weight of ammonium salt of Resin 731. paint produced from this stabilized polymer dispersion Outstanding paints have resulted when the last stabilizwas mobile without agitation, fluid and had no grain after mg mixture was. substituted for a Triton-GMR-S-am- 4freezing cycles. monlum oleate mixture in a poiytner dispersion other Surprisingly, the further stabilized polymer dispersions wise produced in accordance with Example 18. Still of Examples 27 and 28 were found to be stable to multiother mixtures of anionic and/or nonionic emulsifying valent metal ions. It was found that substantial amounts agents-readily apparent to those skilled in the art may also of divalent calcium in the form of calcium chloride and be utilized without in any way departing from the spirit substantial amounts of trivalent aluminum the form of of the invention, since slight variationsof conditions and alum could be added to thesedispersions without coagupigments incorporated will call for slight adjustments in lating the dispersions. Stability of a polymer dispersion stabilization. to multivalent metal ions is particularly advantageous in Effects of varied stabilization of polymer dispersions on a dispersion to be used in producing paint, since a much the freeze characteristics of paints containing such diswider variety of paint pigments may be incorporated in persions are further illustrated by Examples 31-36 which such a dispersion without coagulation. The addlt ion of follow. Ingredients in accordance with the following nonionic emulsifier after completion of polymerlzatlons in 55 recipes were charged into 28 oz. crown capped glass accordance withthe invention appears to be responsible bottle for this desiic-iable result. h h d h Pol mer ispersions w ic pro uce paints aving very little reeze resistance may sometimes be substantially Parts by weight improved by slight alterations of the stabilizing mixture added to the dispersions after polymerizations. Examples Example 31 Example 32 29 and 30 illustrate this fact. The following ingredients were charged into a plant reactor: Butadiene s7 37 Parts by weight figiiga Butadiene 37 7 grs o al I n I 8: t 1. 2 3 gglegoflanhydrous Na2B4O1JOI-I2O g g i 5 The bottles were then capped and rotated end over end a in a 70 C. water bath for 8 hours. The conversions of 9 Y was affected 7 Durlng P Examples 31 and 32 were respectively 95.5% and 97.0%. merizatlon N-acconol'NRSF was in ected mto the reactor The fin l total id f h polymer di i were as vfollows: 0.2 part by weight at 23% total solids, 0.2 i 1 39 4% and 39 9% An alkyl aryl olyether alcohol, a nonionic emulsifier sup- A Portion of the P l P H f Example 31 was plied by" General iline 8: Film Corporation.

further stabilized by adding a mixture of emulsifiers con- Polymerization was completed; the I 9 sistin of 1.5 arts by weight r 100 parts of polymer of ea ch of th following: Trii n X- 100 and Antarox A-400. T' thus stabilized polymer dispersion was then mixed with a paint pigment dispersion. Freeze characto four freezing cycles of a test modified from the test previously described only in that freezing was effected at '25 C. According to the previously described method, viscosity in seconds was determined in the previously teristics of the resulting paint were then determined and described conical brass cup for each ofthe paints prior appear in Table 7 under the designation of Example 33. to freezing and after each of the four freez ng cycles. The

Another portion of the polymer dispersion of Example results of these freeze tests are reported in Table 8.

31 was fur 'ier stabilized by adding a mixture of emulsifiers consisting of 2.2 parts by weght 3f Nalcclogiol NRSE, 1 TABLE 8 1.5 parts by weight of Triton an parts y 0 E ea a Nazi" on aim viscomweight of Antarox A1l00d(all1based am 100 parts of pply g f f g p ty mer). The thus stabi ize po ymer ispersion was me with a paint pigment dispersion identical with that used in WSW? in preparing Example 33. The freeze characteristics of the Example No. 1st 2nd 3 d an r isglg anngppeagrg appear in Table 7 under the designation Original Cycle cycle cycle Cycle A paint was prepared from a portion of the polymer dispersion of Example 32 by emulsifier and paint pigment 8-3 3-2 3-;

dditious identical with those used in preparing Example 11:11:11:11:11:: 1L3 33. The freeze characteristics of this paint appear in 40 9.8 13.0 14.1 14.1 11. Table 7 under the designation of Example 35. Similarly, a Pain? Wa5 PreParcd from another of the l Referring to the data of Table 8, it is apparent that dlsperslon of Exafllple y -l and P the viscosities of the paints produced from Examples pigment dispersion additions identical with those used n 37 40 were only slightly afi t d by long periods of preparing Example 34. The freeze Chara s Of this freezing. The viscosities, even after four freezing cycles, paint appear in Table 7 under the designation of Exwere all well within desired limits. None of these paints ample 36. contained grain even after the fourth cycle.

- TABLE 7 Paint freeze characteristics Example No. 1st; Freeze Cycle 2nd Freeze Cycle 3rd Freeze Cycle 4th Freeze Cycle slightly viscous, no gratin-.- moderately viscou nograin" viscous, 119 grain viscous, slight grain. 34 tiuid, no grain slightly viscous, 110 gram.... slightly viscous, no grain slightly viscous, no g1'8l11. mobile without agitation, d0 moderately viscous, no grain.- moderately viscous, slight tiiiid, no grain. grain. 35 dn mobile without agitation, fluid, no grain fluid, no grain.

fluid, no grain.

Referring to Table 7, it can be seen that the paints of EXAMPLE 41 Examples 33 and 35, though they did not coagulate and showed only slight grain after four freezing cycles, did become viscous. The paint of Example 34, prepared from the same polymer dispersion used in preparing the paint of Example 33, was however only slightly viscous after four freezing cycles. The improved freeze stability resulted from the additional emulsifier (2.2 parts of blacconol NRSF) used in stabilizing the polymer dispersion. Similarly, the freeze characteristics of the paint of Example 36 were substantially better than those for the corresponding paint of Example 35.

Still further illustrations of stable polymer dispersions and paints resulting therefrom are presented by the following additional examples. Another plant scale polymerization was made in accordance with the proportions of ingredients and conditions of the polymerization of Example 18 except that 135 parts of water were initially charged.

Separate portions of the resulting polymer dispersion were further stabilized by adding the following mixtures of emulsifiers:

1 A mixed anionic and nonionic emulsifier supplied by Atlas Powder Company. Wilmington, Delaware.

An anionic emulsifying agent supplied by General Aniline and Film Corporation, New York, New York. I B Supplied by Onyx Chemical Company, Jersey City, New

ersey.

Paints were produced by mixing identical paint pigment dispersions with the stabilized polymer dispersions of Ex- Another plant scale polymerization was carried out by charging the following ingredients into a reactor:

Polymerization was effected at 70 C. At about 60% conversion 2.2 parts by weight of Nacconol NRSF per 100 parts of monomers was injected into the reactor and polymerization completed. A small amount of unreacted butadiene was removed from the resulting latex by stripping. The specific surface of the latex was 42.5 square meters per gram' of polymer. The latex was further stabilized by the addition thereto of 3.0 parts by weight of Triton X-lOO and 3.0 parts by weight of ammonium salt of Resin 731, both per 100 parts by weight of polymer.

A paint was produced by admixing the above stable latex with a paint pigment dispersion. The freeze characteristics of the paint were determined according to the procedure used in Examples 19-36 and are reported as follows:

1.9! freeze cycle-Mobile without agitation, fluid, no grain.

4 th freeze cycle-Mobile without agitation, fluid, no

grain.

EXAMPLE 42 Still another plant scale polymerization was carried out by charging the following ingredients into a reactor:

Parts by weight As in Example 41, polymerization was effected at 70 amples 3740. Each of the resulting paints was subjected C., 2.2 parts of Nacconol NRSF was injected into the 11: reactor at about ,60% conversion and unreacted butadieue was stripped after completion of the polymerization. The specific surface of the resulting latex was 40.75 square meters per gram of polymer. The latex noted that the small amount of borax included in the above rec pe was insufiicient to have an, appreciable buffering action. Thus, the pH of theresulting latex was quite low. For convenience in packaging, commercial was further stabilized by the addition thereto of 3.0 parts 6 paints arc ordinaril neutral or alkaline on by 8)" P P'f by weight of the pH of the late x was increased to 9.4 by diii o ammompm Salt of lmseed 011 fatty E thereto of ammonium hydroxide (28%). When it is A P was P Q Q y admlxlng thlS latex with desired to increasethe pH of acidic latices of the invena Palnt R 8 p P116615 of tion, any ofthe conventional alkaline reagents are suitl'esultlflg palntjyere determlned P sublectlflg Q 10 able, especially morpholine, ammonia or triethanolamine' P to foul" fl'cezlng cycles Q the a stronger base, such as KOH, can be used if suitable y Observed fifter each fl'eellng Cy accofdlng t precautions are taken, as are known to those skilled Procedure 1n P f Afteffoul: freezing in the rubber latex art. The. latext' was additionally cycles, the paint contained no gram.- The viscosities were Stabilized b ddi i of 21 parts b i of as follows: 15 conol NRSF, 3.0 parts by weight of Tl'itOn'X-IOO and vlscoslty Seconds 2.0 parts by weight -of ammonium salt of linseed oil 0r1g1nal v1scos1ty fatty acid, all per .100 parts. by weight of polymer in s fr ng y the latex. The thus stabilized polymer latex was mixed 2nd freemg c1y:1e with an aqueous pigment dispersion to produce a pai t, 3rd ffeellng y The paint was subjected to three freezing cycles at 4th freelmg Cycle and the viscosity of the paint after each of the freez- This paint also had excguent freeze stability. mg cycles was deternuned in accordance with the pro- EXAMPLES 4342 cedure used in Examples 37-40 and 42. The paint was V 25 freeze-stable and after three complete freezing and thaw- A plant scale polymerization i il to E l 42 1ng cycles contained no grain. The viscosities after the r was carried out, exceptthat 1.3 parts of potassium pera 101's freezing cycles were as follows: sulfate was employed and 0.3 part of Nacconol was subviscosit second stituted for the MP-189S. No additional emulsifier original viscosity 3 was injected during polymerization. After polymeriza- 1st freezing, cycle tion samples of the resulting latex were stabilized by 2nd freezing cycle 31.0 addition of varying amounts and types of emulsifying 3rd freezing cycle agents, as is shown in Table 9. The stabilized latices in accordance i bl 9 were h i d i h a In add tion to the general discussion of the invention standard paint pigment masterbatch as in previous set forth in the early part of this specification, experience amples, and the resulting paints were frozen and thawed gained In conducting Specific examples of thfi invenas before. The thawed paints were all satisfactorily fluid reported above and 8180 in Conducting m r us adand possessed viscosities of less than 30 seconds. On ditiollal experiments has made it clear that it y bc the other hand a sample of the original latex containing fur h Characterized as s: no added emulsifying agent was mixed with a portion 40 Other water soluble salts of persulfuric acid may be of the standard paint pigment mastcrbatch to produee a successfully employed in lieu of the potassium persulfate control paintythis control paint coagulated upon freezing of the examples, including sodium, lithium and amand thawing, thus failing the freeze test. monium persulfates.

TABLE 9 Emulsifiers added after conversion PM P Parts 1;, Total Example N0. Nacctfr tol Tri ifi gggg Tr ll 51 1 .235 1 gg;

NRSF X-IOO Fatty Acid X-114' 00 550" mm A non-ionic emulsifier supplied by Rohm dz Haas Company and described as octylphenoxy-polyethoxy-ethanol. "A non-ionic emulsifier supplied by General Aniline 6:

oxyethylated. 118.5 a polyonylphenol.

EXAMPLE 53 As an illustration of production of a paint in accord ance with the invention from alatex produced by polymerization in an acid system, ingredients in accordance with the following recipe were charged into a polymeri zation reactor:

Parts by Weight 7.0

An alkyl sodium sulfonate supplied by E. I. du Pont d Nemours & Co.

Polymerization of the above ingredients was efiected at' C. and was complete after nine hours. The final total solids of the resulting latex was 43.8%. The pH of the latex was 1.95. In this regard it should be I potassium rosin soaps, and the like.

Film Corporation and described In addition to the specific examples and types of anionic emulsifiersmentioned above as suitable for incorporatinginitially in the polymerization recipe, any of the available anionic emulsifiers may be used, including the ordinary soaps (either sodium or potassium soaps) sodium or Soaps as initial emulsifiers, however, have been found to result in slower polymerization rates. Consequently, the other. anionic emulsifiers are to be preferred. As a preferred range, within the broader range of 0.02 to 2.5 parts, the range of 0.1 to 1.3 parts of initial anionic emulsifying agent has been found to result in especially rapid rates of polymerization and to produce latices of relatively high inherent stability.

Polymerization modifiers such as the various aliphatic mercaptans and mixtures thereof, when included in polymerization recipes otherwise in accordance with the invention, have been found toimpair the freeze characteristics of paints produced from the resulting latices. Additionally, the presence of such modifiers greatly retards the polymerization rate and tends to cause undesirable floc. The use of these polymerization modifiers should, therefore, be avoided.

Although the examples relate to copolymers of styrene and 1,3-butadiene only, the mono and di-vinyl benzenes and other 1,3-butadienes may be used as the monomers. The styrenes contemplated are the known derivatives of styrene, including alpha-methylstyrene, the nuclear-substituted styrenes, the various known chlorostyrenes, vinyl toluene and the like. Also contemplated are other known conjugated diolefins, especially including isoprene.

If desired, cross-linking agents may be included in the polymerization formulae of the invention. Di-vinyl benzene has, for example, been successfully included without lowering the rate of conversion or affecting the stability of the resulting aqueous polymer dispersions. The cross-linking agent may be either initially charged into the reactor or it may be subsequently added during polymerization.

The stable latex of the invention, as polymerized, is characterized by a total solids content in the range of 35 to 50% by weight, and preferably in the range of 40 to 50%. The operative range of the proportion of water initially charged is 90 to 150 parts water per 100 parts total monomers, by Weight.

The latex of the invention is characterized by its low particle surface values, as is brought out by the discussion of the specific surface ranges in the early part of this specification. This characteristic of the latex is important in that relatively less stabilizing emulsifying agent is required to make it freeze stable. A resulting copolymer film, or paint film from a water dispersion paint embodying the latex, is more resistant to water and abrasion than comparable films derived from prior latices which required relatively large proportions of hydrophilic emulsifying agents for their mechanical stabilization. Paints of the invention are particularly water resistant if the stabilizing emulsifying agents contained therein include a fugitive soap. A fugitive soap behaves like an ordinary sodium or potassium soap in a water solution, but when such solution is dried the soap gradually decomposes because of evaporation of the cation forming portion thereof. Suitable fugitive soaps are illustrated in the preceding examples and include ammonium and substituted ammonium soaps of various carboxylic acids such as they fatty acids, the rosin acids, the dis-- proportionated rosin acids, the hydrogenated rosin acids and the like, e. g. ammonium olcate, ammonium and morpholinium soaps of rosin acids, ammonium soap of linseed oil fatty acids, and the like. The presence of a soluble phosphate, such as NarPzOv, is desirable in a water dispersion paint to improve its freeze stability, as is brought out above.

Other polymerization reaction temperatures than those shown in the examples have been successfully employed, for example, in the range of 60 to 90 C. Other experiments have made it quite clear that this temperature rangeshould be extended to include the broader range of 40 to 125 C. as the preferred polymerization temperature range for the process of the invention.

The various examples show the production of freezestable latex and paint, according to the invention, by addition of a relatively small quantity of two or more emulsifying agents or of a non-ionic emulsifying agent to the resin latex after 50% polymerization conversion. The examples teach the successful use of less than 1% of added emulsifier(s) based upon the polymer content of the latex, or of several percent in many instances. The total amount of emulsifier(s) added depends upon a number of factors, e. g., a latex possessing a smaller specific surface value requires less added emulsifier to protect it against freezing than a similar latex having a larger specific surface value; exceptional freeze stability requires the addition of more emulsifier than is required for protection against a single freeze; in general,- water resistance of a paint film is improved by use of the minimum quantity of added emulsifier necessary to give the latex and resulting paint the desired freeze resistance.

Changes in the specific details and proportions of ingredients given in the examples may be made without departing from the spirit and scope of the invention, as will be apparent to those skilled in the arts to which this invention is directed.

What is claimed is:

I. A freeze stable water dispersion paint consisting essentially of a stable latex of an aqueous emulsion copolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per. 100 parts by weight of monomers, at a pH in the range of 7.0 to 12.0, and water-d sposed paint pigment admixed with the latex, said paint pigment being water-dispersed by a pigment dispersing agent and said dispersion paint containing a relatively small quantity of more than one additional stabilizing emulsifying agent added to said latex after polymerization conversion and before admixing with said water-dispersed paint pigment, the additional emulsifying agents beingselected from the group consisting of anionic and nonionic emulsifiers.

2. A freeze stable water dispersion paint consisting essentially of a stable latex of an aqueous emulsion c0- polymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per 100 parts by weight of monomers, at a pH in the range of 7.0 to 12.0, the latex characterized by a specific surface in the range of 3 to square meters per gram of dry copolymer, and water-dispersed paint pigment admixed with the latex, said paint containing a relatively small quantity of more than one additional stabilizing emulsifying agent added to said latex after 50% polymerization conversion and before admixing with said water-dispersed paint pigment, at least one of the additional emulsifying agents being an anionic emulsifier.

3. A freeze stable water-dispersion paint consisting essentially of a stable latex of an aqueous emulsion copolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per 100 parts by weight of monomers, at a pH in the range of 7.0 to 12.0, the latex characterized by a specific surface in the range of 3 to 60 square meters per gram of dry copolymer, and Waterdispersed paint pigment admixed with the latex, said paint containing a relatively small quantity of, more than one additional stabilizing emulsifying agent added to said latex after-50% polymerization conversion and before admixing with said water-dispersed paint pigment, at least one of the additional emulsifying agents being a nonionic emulsifier.

4. A freeze stable water dispersion paint consisting essentially of a stable latex of an aqueous emulsion copolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,-3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per parts by weight of monomers, at a pH in therange of 7.0 to 12.0, the latex characterized by a specific surface in the range of 3 to 60 square meters per gram of dry copolymer, and water-dis' persed paint pigment admixed with the latex, said paint containing a relatively small quantity of a mixture of nonionic and anionic emulsifying agents added to said latex after 50% polymerization conversion and before admixing with said water-dispersed paint pigment.

5. A freeze stable latex of an aqueous emulsion copolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per 100 parts by weightof monomers, at a pH in the range of 7.0 to 12.0, the latex characterized by a specific surface in'the range of 3 to presence ,of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02v to 2.5 parts initial'charge of an anionic emulsifying agent. per 100 parts by weight of monomers, at a pH in the range of 7.0 to 12.0, the latex characterized by a specific surface in the range of '3 to 60 square meters per gram of dry copolymer, said latex containing a relatively small quantity of more than one presence of about 1.0 to 2.0 parts of'a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per 100 parts by weight of monomers, at a pH in the range of 7.0 to 12.0, the latex characterized by a specific surface in the range of 3 to 60 square meters per gram of dry copolymer, said latex containing a relatively small quantity of more than one additional stabilizing emulsifying agent, the additional emulsifying agents including at least one nonionic emulsitying agent added to the latex after 50% polymerization conversion.

8. A freeze stable latex of an aqueous emulsion copolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent,'per 100 parts by weight of monomers, at a pH in the range of 7.0 to 12.0, the latex characterized by a specific surface in the range of 3 to 60 square meters per gram of dry copolymer, said latex containing a relatively small quantity of a mixture of anionic and nonionioemulsifying agents added to the latex after 50% polymerization conversion.

9. A method of producing a freeze stable water-dispersion paint 'co'mprising polymerizing .61 to 73% by weight of a styrene with correspondingly 39 to 27% of a conjugated diolefin, in aqueous emulsion in the presence of about 1.0 to 2.0 partsof a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent per 100 parts by weight of monomers to produce a latex, addinga relatively small quantity of more latex and thereafter admixing said latex with a water-dispersed paint pigment, the additional emulsifying agents being added after 50% polymerization conversion and being selected from the group consisting of anionic and nonionic emulsifiers.

10. A method of producing a freeze stable latex comprising polymerizing 61 to 73% by weight of a styrene with correspondingly 39 to 27% of a conjugated diolefin, in aqueous emulsion in the presence of about'1.0 to 2.0 parts of a soluble salt of persulfuricacid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent per 100 parts by weight of monomers to produce a latex and adding a relatively small quantity of more than one additional stabilizing emulsifying agent to said latex after 50% polymerization conversion, the additional emulsifying.

'the range of 40 to 50% by weight, said latex containing a relatively small quantity of more than one additional stabilizing emulsifying agent, the additional emulsifying agents being added to the latex after about 50% polymerization conversion and the additional emulsifying agents being selected from the group consisting of anionic and nonionic emulsifiers. 12. A freeze stable latex of an equeous'emulsion copolymer of about 63% by weight of styrene and about 37% 1,3-butadiene polymerized in the presence of 1.0 to 2.0 parts of potassium persulfate, 0.1 to 1.3 parts initial charge of an anionic emulsifying agent and 90 to 150 parts initial charge of water, per 100 parts by weight of monomers, the polymerization conducted in the pH range of ,than one additional stabilizing emulsifying agent to said 1s 8.0 to 10.0 and the total solids of the latex being'in the range of 40 to 50% by weight, said latex'contarnrng NarPzOr and a relatively small quantity of more than one additional emulsifying agent, the additional emulsifying agents being added to said latex after about 50% polymerrzatron conversion and the additional emulsifying agents belng selected from the group consisting of anionic and nonionic emulsifiers.

13. A freeze stable latex of an aqueous emulsioncopolymer of about 63% by weight of styrene and about 37% 1,3-butadiene polymerized in the presence of 1.0 to 2.0 parts of potassium persulfate, 0.1 to 1.3 parts initial charge of an anionic emulsifying agent and to 150 parts initial charge of water, perparts bv weight of monomers, the polymerization conducted in the pH range V of 8.0 to 10.0 and the total solids of the latex being in the range of 40 to 50% by weight, said latex containing Na2B40'1 and a relatively small quantity of more than one additional stabilizing emuIsif-yingagent, the additional emulsifying agents being added to said latex after about 50% polymerization conversion and the additional emulsifying agents being selected from the group consisting of anionic and nonionic emulsifiers.

14. A freeze stable waterv dispersion paint consisting essentially of a stable latex of an aqueous emulsion copolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per 100parts. by weight of I monomers, and water-dispersed paint pigment admixed with the latex, said paint pigment being water-dispersed by a pigment dispersing agent and said dispersion paint con-. taining a relatively small quantity of more than one additional stabilizing emulsifying agent added to said latex= after 50% polymerization conversion and before admixing with said water-dispersed paint pigment, the additional emulsifying agents being selected from the group consisting of anionic and nonionic emulsifiers.

15. A freeze stable latex of an aqueous emulsion copolymer of 61 to 73% by weight of styrene and .correspondingly 39 to 27% 1,3-butadieni: polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per 100 parts by weight of monomers, said latex containing a relatively small quantity of more than one additional stabilizing emulsifying agent added to the latex after 5 0% polymerization con-. version, the additronalemulsrfymg agents being selected fggm the group consisting of anionic and nonionic emul s ers.

16. A freeze stable water dispersion paint consisting essentially of a stable latex of an aqueous emulsion copolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in,

the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of 17. A freeze stable latex of an aqueous emulsion. copolymer of 61 to 73% by weight of styrene and correv spondingly 39 'to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 .to 2.5 parts initial charge of an anionic emulsifying. agent, per 100 parts by weight of monomers, said latex containing a relatively small quan-,

tity of more than one additional stabilizing emulsifying I agent added to the latex after 50% polymerization conversion, at least one of said emulsifying agents being an alkyl aryl polyether alcohol.

18. A freeze stable water dispersion paint consisting essentially of a stable latex of an aqueous emulsion copolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of 1 ananionic emulsifying agent, per 100 parts by weight of monomers, and water-dispersed paint pigment admixed with the latex, said paint pigment being waterdispersed by a pigment dispersing agent and said dispersion paint containing a relatively small qu ant1ty of more than one additional stabilizing emulsifying agent added to said latex after 50% polymerization conversion and before admixing with said waterdispersed paint pigment, at least one of said emulsifying agents being an alkyl aryl sulfonate.

19. A freeze stable latex of an aqueous emulslon copolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per 100 parts by weight of monomers, said latex containing a relatively small quantity of more than one additional stabilizing emulsifying agent added to the latex after 50% polymerization conversion, at least one of said emulsifying agents being an alkyl aryl sulfonate.

20. A freeze stable latex of an aqueous emulsion copolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per 100 parts by weight of monomers, said latex containing a relatively small quantity of more than one additional stabilizing emulsifying agent added to the latex after 50% polymerization conversion, at least one of said emulsifying agents being a fugitive soap selected from ammonium and substituted ammonium soaps of carboxylic acids.

21. A freeze stable water dispersion paint consisting essentially of a stable latex of an aqueous emulsion copolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per 100 parts by weight of monomers, at a pH in the range of 7.0 to 12.0, the latex characterized by a specific surface in the range of 3 to 60 square meters per gram of dry copolymer, and waterdispersed paint pigment admixed with the latex, said paint containing a relatively small quantity of more than one additional stabilizing emulsifying agent added to said latex after polymerization and before admixing with said water-dispersed paint pigment, the additional emulsifying agents being selected from the group consisting of anionic and nonionic emulsifiers.

22. A freeze stable latex of an aqueous emulsion ccpolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per 100 parts by weight of monomers, at a pH in the range of 7.0 to 12.0, the latex characterized by a specific surface in the range of 3 to 60 square meters per gram of dry copolymer, said latex containing a relatively small quantity of more than one additional stabilizing emulsifying agent added to the latex after polymerization, the additional emulsifying agents being selected from the group consisting of anionic and nonionic emulsifiers.

23. A freeze stable latex of an aqueous emulsion copolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per 100 parts by weight of monomers, said latex containing a relatively small quantity of an additional stabilizing emulsifying agent added to the latex after 50% polymerization conversion said additional stabilizing emulsifying agent being a nomomc emulsifier.

24. A freeze stable latex of an aqueous emulsion copolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of asoluble salt of a persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per parts by weight of monomers, said latex containing a relatively small quantity of an additional stabilizing emulsifying agent added to the latex after 50% polymerization conversion, said additional stabilizing emulsifying agent being an alkyl aryl polyether alcohol.

25. A freeze stable water-dispersion paint consisting essentially of a stable latex of an aqueous emulsion copolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per 100 parts by weight of monomers, and water-dispersed paint pigment admixed with the latex, said paint pigment being water-dispersed by a pigment dispersing agent and said dispersion paint containing a relatively small quantity of an additional stabilizing emulsifying agent added to said latex after 50% polymerization conversion and before admixing with said water-dispersed paint pigment, said additional stabilizing emulsifying agent being a nonionic emulsifier.

26. A freeze stable water-dispersed paint consisting essentially of a stable latex of an aqueous emulsion copolymer of 61 to 73% by weight of styrene and correspondingly 39 to 27% 1,3-butadiene polymerized in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent, per 100 parts by weight of monomers, and water-dispersed paint pigment admixed with the latex, said paint pigment being water-dispersed by pigment dispersing agent and said dispersion paint containing a relatively small quantity of an additional stabilizing emulsifying agent added to said.latex after 50% polymerization conversion and before admixing with said water-dispersing paint pigment, said additional stabilizing emulsifying agent being an alkyl aryl polyether alcohol.

27. A method of producing a freeze stable latex comprising polymerizing 61 to 73% by weight of a styrene with correspondingly 39 to 27% of a conjugated diolefin, in aqueous emulsion in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent to produce a latex, and adding a relatively small quantity of an additional stabilizing emulsifying agent to the latex after 50% polymerization conversion, said additional stabilizing emulsifying agent being a nonionic emulsifier.

28. A method of producing a freeze stable water dispersion paint comprising polymerizing 61 to' 73% by weight of a styrene with correspondingly 39 to 27% of a conjugated diolefin, in aqueous emulsion in the presence of about 1.0 to 2.0 parts of a soluble salt of persulfuric acid and 0.02 to 2.5 parts initial charge of an anionic emulsifying agent to produce a latex, adding a relatively small quantity of an additional stabilizing emulsifying agent to the latex after 50% polymerization conversion, said additional stabilizing emulsifying agent being a nonionic emulsifier, and thereafter admixing said latex with water-dispersed paint pigment.

No references cited. 

1. A FREEZE STABLE WATER DISPERSION PAINT CONSISTING ESSENTIALLY OF A STABLE LATEX OF AN AQUEOUS EMULSION COPOLYMER OF 61 TO 73% BY WEIGHT OF STYRENE AND CORRESPONDINGLY 39 TO 27% 1,3-BUTADIENE OF A SOLUBLE SALT OF PRESENCE OF ABOUT 1.0 TO 2.0 PARTS OF A SOLUBLE SALT OF PERSULFURIC ACID AND 0.02 TO 2.5 PARTS INITIAL CHARGE OF AN ANIONIC EMULSIFYING AGENT, PER 100 PARTS BY WEIGHT OF MONOMERS, AT A PH IN THE RANGE OF 7.0 TO 12.0, AND WATER-DISPOSED PAINT PIGMENT ADMIXED WITH THE LATEX, SAID PAINT PIGMENT BEING WATER-DISPERSED BY A PIGMENT DISPERSING AGENT AND SAID DISPERSION PAINT CONTAINING A RELATIVELY SMALL QUANTITY OF MORE THAN ONE ADDITIONAL STABILIZING EMULSIFYING AGENT ADDED TO SAID LATEX AFTER 50% POLYMERIZATION CONVERSION AND BEFORE ADMIXING WITH SAID WATER-DISPERSED PAINT PIGMENT, THE ADDITIONAL EMULSIFYING AGENTS BEING SELECTED FROM THE GROUP CONSISTING OF ANIONIC AND NONIONIC EMULSIFIERS. 